This invention relates to the measurement of pressure in high-temperature liquids. It is especially useful for measuring pressure in liquid metals such as liquid sodium or liquid potassium.
Operation of a liquid-metal fast breeder reactor requires information about the pressure of the liquid metal over a range of gage pressures from zero to more than 300 lbs. per square inch (2MPa) and at temperatures ranging from 700.degree.-800.degree. F. (644-700 K) at the inlet to 1000.degree.-1200.degree. F. (810-922 K) at the outlet. Such pressures have in the past been measured by a metal diaphragm exposed on one side to the pressure to be measured and on the other side to an externally applied pressure of air or some other convenient gas. To operate the gage, gas pressure is applied to one side of the diaphragm to cause it to achieve a neutral position. If areas are equal on both sides of the diaphragm, then the pressure necessary to place the diaphragm in the neutral position is the pressure of the liquid metal. If the areas differ, then the pressures are in the inverse ratio of the areas. Operation then comprises cycling the pressure up and down for small amounts about the mean valve over a period of a few seconds. If the test pressure has changed since the reference pressure was set, then this cycling will cause the diaphragm to assume a different mean position. The new pressure is then determined by changing the reference pressure to restore the neutral position of the diaphragm. This process takes a time of the order of half a minute to make a measurement, and the measurement is ambiguous if the pressure being measured is not constant during that half minute. The calibration also varies over time as the spring constant of the diaphragm changes from thermal stress or corrosion.
It is an object of the present invention to provide a better means of sensing pressure in high-temperature liquids.
It is a further object of the present invention to provide a means for sensing pressure in high-temperature liquids, which means can be calibrated quickly in situ.
Other objects will become apparent in the course of a detailed description of the invention.